/* Copyright  2009
   @Author
   Richard Changde Yin            e-mail yinchangde@hotmail.com

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; version 2 of the License.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software
   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA */

/**
 * @filename: internal_error_handler.h
 */

#ifndef __INTERNAL_ERROR_HANDLER_H__
#define __INTERNAL_ERROR_HANDLER_H__



/**
  This class represents the interface for internal error handlers.
  Internal error handlers are exception handlers used by the server
  implementation.
*/
class Internal_error_handler
{
protected:
  Internal_error_handler() {}
  virtual ~Internal_error_handler() {}

public:
  /**
    Handle an error condition.
    This method can be implemented by a subclass to achieve any of the
    following:
    - mask an error internally, prevent exposing it to the user,
    - mask an error and throw another one instead.
    When this method returns true, the error condition is considered
    'handled', and will not be propagated to upper layers.
    It is the responsibility of the code installing an internal handler
    to then check for trapped conditions, and implement logic to recover
    from the anticipated conditions trapped during runtime.

    This mechanism is similar to C++ try/throw/catch:
    - 'try' correspond to <code>Session::push_internal_handler()</code>,
    - 'throw' correspond to <code>my_error()</code>,
    which invokes <code>db_message_sql_hook()</code>,
    - 'catch' correspond to checking how/if an internal handler was invoked,
    before removing it from the exception stack with
    <code>Session::pop_internal_handler()</code>.

    @param sql_errno the error number
    @param level the error level
    @param session the calling thread
    @return true if the error is handled
  */
  virtual bool handle_error(uint32_t sql_errno,
                            const char *message,
                            COLLAPSAR_ERROR::enum_warning_level level,
                            Session *session) = 0;
};
#endif /* __INTERNAL_ERROR_HANDLER_H__ */
